The significance of membership in the Schengen Agreement is that on the one hand member states do not carry out border checks at their internal borders and on the other hand member states have established controls with clearly defined criteria at their external borders.

Furthermore, member states have set up a common visa policy for short stays (namely for stays up to three months), which is applied through the ‘Schengen visas’.

Citizens of some non-EU countries are required to hold a visa to travel to the Schengen area. A short-stay visa issued by one of the member states of the Schengen area entitles the holder to travel throughout the whole Schengen area for up to three months within a six-month period. However, visas for visits exceeding that three-month period remain subject to national procedures.

Is Schengen dead?

The biggest migratory wave of the last 70 years has put the Schengen treaty under great pressure and the terror in Paris has only increased the crisis.

"Saving Schengen is a race against time, and we are determined to win that race. Without effective control on our external borders, the Schengen rules will not survive," said Tusk, president of the European Council.

Is Schengen really so important?

Border-free travel has been one of the great achievements for European citizens as well as for foreign travellers since the establishment of the Schengen zone 30 years ago. Free movement of people throughout the Schengen area is one of the four principals of freedom underpinning the European Union in the Treaty of Rome. You can move freely across 26 European countries, allowing you to travel 3,000 km from Poland to Portugal without having to show your papers once.

“The concept of a Europe without borders has become very difficult for governments to defend,” wrote Stratfor, in a geopolitical analysis following the Paris attacks.

If citizens feel threatened, governments may be tempted simply to re-erect the barriers. France and Germany have ramped up border controls. But that ignores the real costs involved in reversing decades of European integration. Several studies have proved that Schengen has led to closer trading partnerships — increasing imports and exports. It has also boosted tourism. Schengen might be considered the most visible manifestations of European unity.

"It is highly likely we will have to adjust the fundamental treaties of the EU. The Schengen treaty begs for correction” said Viktor Orban, Hungarian prime minister.

Schengen is not dead but a dead end in its present form. Schengen should preserve the freedom of internal free movement but also should protect its outer border. “If you cannot protect your borders, you cannot protect your territory, and you cannot protect your citizens.” said the Hungarian foreign minister.

The solution is not to abandon Schengen, but to strengthen the external border control.